Preliminary Report of a Method for Estimating in Vivo the Germicidal Activity of Antiseptics

Abstract

DURING the past month at the Pennsylvania Hospital we have been trying to develop a method by which we could estimate the germicidal activity of antiseptics in infected wounds.The method of estimating and graphically recording the bacterial contents of a wound with the microbe charts works out well clinically, but the results are, at best, a very crude determination, because the area of the smear examined (counting IO or 20 fields thrQugh a '/,2-inch oil-inmmersion lens) contains a very small proportion of the microbes removed from the wound on the platinum loop. Be the smear as smooth and even as is humanly possible to make it, the margin of error is still very large. With a view to reducing this margin of error we have been culturing the wounds, counting the number of colonies and plotting curves as in the microbe charts mentioned above. Admitting that there is still much to be desired, in that the size of the drop obtained on the loop is still a variable quantity, we feel that we have a very much truer estimation of the bacterial content of the wound than when using the smear method.In order to reduce as far as possible the element of the personal equation, the work has been done by one man. The inoculations were made from the same part of the surface of the wound, one definite spot being selected and used throughout; the attempt was made to get a uniform-sized drop; the same platinum wire loop was used each time. The drop obtained was inoculated at the bedside in 2 c.c. of plain bouillon, the bouillon suspension, undiluted, was immediately poured over an agar-agar plate, which was then covered and turned upside down and marked with the patient's number, the number of the culture, and the time the culture was taken. The plate was then taken to the laboratory and placed in an incubator and kept at thirty-seven degrees C. At the end of twenty-four hours the colonies were counted, macroscopically, and recorded.The first case, an incised carbuncle with several discharging sinuses, gave, as you will see on Fig. I, rather irregular curves. We believe that as the patient turned about in bed during the day some sinus discharged pus and bacteria which ran over the area from which the inoculations were taken, a point on the surface of the bottom of the wound and in the centre of the star, reinoculating that area and, therefore, giving a very 16 241